Comprehensive Description
(
Inglês
)
fornecido por Smithsonian Contributions to Zoology
Steindachnerina bimaculata (Steindachner, 1876)
Curimatus bimaculatus Steindachner, 1876:76 [type locality: Brazil: Hyavary (= Rio Javarí); ? mouth of Rio Negro].—Eigenmann and Eigenmann, 1889:422 [Brazil: Hyavary (= Río Javarí), Coary (= Coarí), Villa Bella; not specimens from Ica (= Río Içá)].—1891:47 [reference].—Pellegrin, 1909:148 [Brazil: Tonantins].—Eigenmann, 1910:421 [references in part, not Río Paraguay basin citations].—Vari, 1989a, tables 2, 3 [assignment to Steindachnerina].—[not Boulenger, 1900:2; Eigenmann and Kennedy, 1903:511; Eigenmann and Ogle, 1907:3; Eigenmann, McAtee, and Ward, 1907:124; Bertoni, 1914:9].
Curimaius trachystetus Cope, 1878:684 [type locality: Peruvian Amazon].—Vari, 1989a, tables 2, 3 [assignment to Steindachnerina].
Curimaius bímaculatus sialis Eigenmann and Eigenmann, 1889:422 [type locality: Brazil: Manacapuru].—1891:47 [reference].—Eigenmann, 1910:421 [reference].—Vari,1989a, tables 2, 3 [assignment to Steindachnerina].
Curimaius bimaculatus trachystetus.—Eigenmann and Eigenmann, 1889:422 {Curimaius trachystetus Cope, 1878, placed as a subspecies; Amazon basin, Serpa (= Itacoatiara, Brazil) to Peru].—1891:47 [reference].—Eigenmann, 1910:421 [reference].
Curimata trachystetus.—Fowler, 1906:299, fig. 5 [based on holotype of Curimatus trachystetus; designated as type species of subgenus Steindachnerina Fowler].—1942b:209 [reference].—1945:117 [reference].
Prochilodus pterostigma Fowler, 1913:520, fig. 3 [type locality: Brazil: Rio Madeira about 20 miles north of Porto Velho].—1940b:68 [as a probable synonym of Curimata bimaculala].—1941:164 [assigned to Curimata; hypothesized to be related to Curimata elegans Steindachner].—Géry, 1965:35 [assigned to Curimata].—1972b:32 [as a synonym of Curimata bimaculata].—Vari and Castro, 1988:779 [as a synonym of Steindachnerina bimaculata].—Vari, 1989a, tables 2, 3 [assignment to Steindachnerina].
Curimatus semiornatus Steindachner, 1914:262 [type locality: Brazil: Rio Negro].—1917:20, pl. 5, fig. 5 [Rio Negro].—Fernández-Yépez, 1948:73 [reference].—Vari, 1989a, tables 2, 3 [assignment to Steindachnerina].
Curimata bimaculatus.—Pearson, 1937:109 [in part, Río Mamoré basin references].
Curimata melaniris Fowler, 1940a:253, fig. 54 [type locality: Peru: Río Ucayali, Boca Chica].—Eigenmann and Allen, 1942:299 [reference].—Fowler, 1942b:207 [reference].—1945:115 [reference].—1950:287, fig. 344 [literature compilation].—Vari, 1989a, tables 2, 3 [assignment to Steindachnerina].
Curimata pterostigma.—Fowler, 1941:164 [removed from Prochilodus; related to Curimata elegans].—Fernández-Yépez, 1948:72 [as a possible species of Pseudocurimata Fernández-Yépez].—Fowler, 1950:290, fig. 348 (literature compilation].
Curimata bimaculata.—Eigenmann and Allen, 1942:292 [Peru: Río Morona, Yurimaguas].—Fowler, 1945:118 [reference].—Terasas-Urquidi, 1970:31 [reference].—[not Bertoni, 1939:54].
Curimata trachyslela.—Eigenmann and Allen, 1942:293 [reference].—Fowler, 1950:293, fig. 354 [literature compilation].
Cruxentina bimaculala.—Fernández-Yépez, 1948:53 [assignment to Cruxentina; not cited Alto Paraná references].
Cruxentina bimaculala sialis.—Fernández-Yépez, 1948:53 [assignment to Cruxentina].—Fowler, 1975:367 [reference].
Rivasella melanira.—Fernández-Yépez, 1948:56 [assignment to Rivasella].
Steindachnerina trachyslelha.—Fernández-Yépez, 1948:58, fig. 30 [reference].—Fowler, 1975:375 [reference].
Curimata bimaculata bimaculata.—Fowler, 1950:278 [references in pan, not Paraguay citations].—[not Ringuelet and Aramburu, 1961:36; Lopez et al., 1987:19].
Curimata bimaculata sialis.—Fowler, 1950:279 [literature compilation].
Curimata semiornata.—Fowler, 1950:292 [literature compilation].—1975:369 [reference].—Junk et al., 1983:406 [Rio Amazonas, Ilha de Marchantaria, Lago Camaleao].
Pseudocurimata bimaculata.—Ringuelet, 1975:61 [in part, Amazon basin citation].—[not Aramburu, Aramburu, and Ringuelet, 1962:227; Bonnetto et al., 1978:17; Pignalberi de Hassan and Cordiviola de Yuan. 1985:21; Cordiviola de Yuan and Pignalberi de Hassan, 1985:215].
Cruxentina bimaculatus bimaculatus.—Fowler, 1975:367 [reference].
Pseudocurimata pterostigma.—Fowler, 1975:373 [reference].
DIAGNOSIS.—The presence of three weakly developed longitudinal folds on the roof of the oral cavity rather than three very fleshy flaps and/or one or more series of lobulate fleshy processes in that region discriminates Steindachnerina bimaculata from other members of the genus with the exception of S. binotata, S. leucisca, S. argentea, and S. conspersa. The 43 to 49 scales along the lateral line from the supracleithrum to the hypural joint separate S. bimaculata from S. binotala and S. leucisca, which have 53 or more lateral line scales, and from S. argentea and S. conspersa, which have 43 or fewer scales in that series. Steindachnerina bimaculata is most similar to its allopatric congener S. conspersa. In addition to differing in the number of scales in a series along the lateral line, the species differ in details of pigmentation. Steindachnerina bimaculata typically has a series of small dark spots on the dorsal and dorsolateral surfaces of the body, with the pigmentation around the base of the dorsal fin of the same overall intensity as in proximate portions of the body. Specimens of S. conspersa, in contrast, lack the small dark spots on the body and typically have the region proximate to the base of the dorsal fin much lighter than neighboring regions of the body.
DESCRIPTION.—Body moderately elongate, somewhat compressed, less so in larger specimens; specimens from Río Orinoco basin with somewhat shallower bodies. Dorsal profile of head straight or very slightly concave. Dorsal profile of body smoothly curved from rear of head to origin of dorsal fin, somewhat more convex in larger specimens; straight and posteroventrally slanted at base of dorsal fin; straight or gently convex from base of last dorsal-fin ray to caudal peduncle. Dorsal surface of body with indistinct median keel from rear of head to anterior of dorsal fin, keel more obvious posteriorly; body surface smoothly rounded transversely posterior to fin. Ventral profile of body straight or gently curved from tip of lower jaw to vertical line through origin of pectoral fin, gently curved from that point to origin of anal fin, sigmoid from origin of anal fin to caudal peduncle. Prepelvic region obtusely flattened, with rounded lateral keels; keels most distinct proximate to origin of pelvic fins. Obtuse median keel posterior to pelvic-fin origin. Secondary obtuse keel on each side of postpelvic portion of body about two scales dorsal of ventral midline.
Greatest depth of body 0.30–0.37 [0.36]; snout tip to origin of dorsal fin 0.45–0.51 [0.50]; snout tip to origin of anal fin 0.80–0.87 [0.82]; snout tip to origin of pelvic fin 0.49–0.55 [0.52]; snout tip to anus 0.75–0.83 [0.80]; origin of dorsal fin to hypural joint 0.56–0.62 [0.59]. Dorsal-fin profile acute, less so with increasing age; anteriormost rays 2.5–3.2 times length of ultimate ray. Pectoral-fin profile acute; length of pectoral fin 0.18–0.22 [0.18], extends nearly to vertical line through origin of pelvic fin in smaller individuals, only three-quarters of that distance in largest specimens examined. Pelvic-fin profile acute, length of pelvic fin 0.23–0.27 [0.26], reaches three-quarters distance to origin of anal fin. Caudal fin forked. Adipose fin well developed. Border of anal fin distinctly emarginate, anteriormost branched rays approximately three times length of ultimate ray. Caudal peduncle depth 0.12–0.13 [0.13].
Head distinctly pointed in profile, head length 025–0.30 [0.27]; upper jaw slightly longer, mouth subterminal; anterior portion of buccopharyngeal complex consisting of three weakly developed fleshy folds on roof of oral cavity, without fleshy lobulate bodies; snout length 0.27–0.32 [0.31]; nostrils very close, anterior circular, posterior crescent-shaped, with aperture closed by thin flap of skin separating nares; orbital diameter 0.30–0.36 [0.30]; adipose eyelid present, with vertically ovoid opening over center of eye; length of postorbital portion of head 0.38–0.44 [0.44]; gape width 0.29–0.35 [0.33]; interorbital width 0.41–0.46 [0.46].
Pored lateral-line scales to hypural joint 43 to 49 [45]; all scales of lateral line pored, canals in scales straight; 3 to 5 series of scales extend beyond hypural joint onto caudal-fin base; 7½ to 9 [9] scales in transverse series from origin of dorsal fin to lateral line; 5½ to 6 [6] scales in transverse series from lateral line to origin of anal fin.
Dorsal-fin rays ii,9 or iii,9 (when three unbranched rays present, first very short) [iii,9]; anal-fin rays ii,7 or iii,7 (when three unbranched rays present, first very short) [iii,7]; pectoral-fin rays 14 to 16 [15]; pelvic-fin rays i,8 [i,8].
Total vertebrae 33 (10), 34 (47), 35 (32).
COLOR IN ALCOHOL.—Specimens retaining guanine on scales silvery, darker on dorsal portions of head and body. Overall ground coloration in specimens fixed in formalin and lacking guanine on scales light tan to brown, darker on dorsal portions of head and body. Distinct dusky, deep-lying, narrow band extends along mid-lateral surface of body from supracleithrum to caudal peduncle. Series of small spots of varying degrees of darkness on dorsal and dorsolateral portions of body in most individuals (Figure 24); spots less apparent in some Amazonian specimens and most population samples from Río Orinoco basin (Figure 25; see also comments under “Variation” below). Each spot one-third to one-half size of pupil. When dark spots present, a single longitudinal series apparent in specimens of approximately 40 mm SL; two incomplete series present in larger specimens. Discrete, very dark, saddle-shaped spot along dorsal midline immediately anterior of origin of dorsal fin. Spot more extensive transversely, straddles keel along dorsal midline. Second, somewhat longitudinally elongate, spot along dorsal midline one or two scales posterior of tip of supraoccipital spine. Dorsal fin with spot of dark pigmentation situated on basal portion of middle rays and their associated membranes. Spot most apparent and proportionally larger in specimens under 40 mm SL; becoming progressively more diffuse and less apparent in larger individuals. Anterior and distal margins of dorsal fin dusky in larger specimens. Small but distinct spot of dark pigmentation at base of middle rays of caudal fin; spot sometimes very faint or lacking in specimens under 30 mm SL and in most individuals from Río Orinoco basin (Figure 25), most prominent when present in larger individuals. Lower lobe of caudal fin dusky. Anal fin with series of small scattered chromatophores.
DISTRIBUTION.—Río Orinoco and Río Amazonas basins (Figure 23).
VARIATION.—There is a notable degree of variation in body form and dark pigmentation on the body and fins between samples of Steindachnerina bimaculata originating in the Rio Amazonas basin and those from the Río Orinoco system. A less-pronounced degree of variation occurs in the intensity of the pigmentation within the Amazon basin populations. The significance of these differences is difficult to evaluate as a consequence of the limited available population samples from the Río Orinoco system, and the large geographic gap in the distribution of the specimens herein considered S. bimaculata (Figure 23).
Individuals from the Río Orinoco system tend to have shallower bodies than comparably sized specimens from the Amazon basin. The degree of development of both the series of irregular spots located on the dorsolateral surface of the body, and of the patches of dark pigmentation at the base of the dorsal and caudal fins also varies between the two river basins. Specimens from the Rio Amazonas system typically have one or more series of spots on the body and relatively obvious spots at the base of the fins (Figure 24). Available population samples from the Río Orinoco basin, in contrast, usually have fainter spots, with the body and fin spots in some individuals totally absent (Figure 25). Nonetheless, some individuals from the Amazon system also have weakly developed body and fin pigmentation approximating that found in Río Orinoco specimens. Unfortunately the sample of Steindachnerina bimaculata from the Río Orinoco system consists of juveniles making it impossible to determine at this time whether the spots on the body and fins in adults of S. bimaculata from that basin differ from the conditions typical of Amazonian populations of the species. Until such time as additional population samples from the Río Orinoco basin are available, it is premature to recognize these differences formally.
DISTRIBUTION.—Atlantic coastal drainages of Rio Grande do Sul, Brazil; Uruguay; Río Uruguai in Santa Catarina, Brazil; lower Río Paraná, lower Río Paraguay (Figure 23). Braga and Azpelicueta (1987, fig. 3) also report this species from short coastal rivers emptying into the Río de La Plata southeast of Buenos Aires.
COMPARISONS.—Only three other species of Steindachnerina (conspersa, brevipinna, and insculpta) are recognized in this study from within the general region of the known range of S. biornata. Steindachnerina biornata is readily distinguished from S. brevipinna and S. insculpta by its lack of numerous lobulate processes on the roof of the oral cavity, and by details of pigmentation (compare figures of the species). Steindachnerina conspersa is readily discriminated from S. biornata in various details of pigmentation (compare Figures 21 and 22 with Figures 26 and 27) and in its lack of the three well-developed fleshy flaps on the roof of the oral cavity.
MATERIAL EXAMINED.—39 specimens (34, 31.2–73.4).
BRAZIL. Rio Grande do Sul: Rio Jacuí, at bridge on road between Santa Maria and Vera Cruz (−29°41′S, 53°19′W), MZUSP 37133, 1, (73.4; holotype of Curimata stigmosa); USNM 285194, 12 (36.9–59.7, paratypes of Curimata stigmosa, one specimen cleared and counterstained for cartilage and bone); MCP 9613, 4 (43.4–62.8, paratypes of Curimata stigmosa); MZUSP 37134, 7 (34.7–43.4; paratypes of Curimata stigmosa). Rio Forqueta, at Marquês de Souza, Municipio de Lajeado, USNM 285192, 1 (53.7; paratype of Curimata stigmosa); MZUSP 21721, 1 (53.4; paratype of Curimata stigmosa). Arroio Sarandi, along highway (Br 116) between Pelotas and Jaguarão, MZUSP 21728, 1 (43.0; paratype of Curimata stigmosa). Arroio Chasqueiro, along highway (Br 116) between Pelotas and Jaguarão, USNM 285190, 2 (43.5–56.5; paratypes of Curimata stigmosa). Santa Catarina: Pools along Río Uruguai, near Concórdia, MZUSP 285242, 2 (2, 71.5–72.3). Posasdo Rio Uruguai, Divisa Rio Grande do Sul, Concordia, MZUSP 28252, 1 (31.2).
URUGUAY. Florida: Arroio Chamizo, USNM 285192, 2 (64.2–70.4).
ARGENTINA. Entre Ríos: SU 31599, 2. Río Paraguay, USNM 295341, 1. Buenos Aires: no specific location, USNM 176008, 1. Río de La Plata, San Pedro, USNM 295354, 1.
- citação bibliográfica
- Vari, Richard P. 1991. "Systematics of the neotropical characiform genus Steindachnerina Fowler (Pisces: Ostariophysi)." Smithsonian Contributions to Zoology. 1-118. https://doi.org/10.5479/si.00810282.507